Sunday, March 25, 2012

Line drilling carb bodies for new shafts

Last night, I figured out a simple way to drill out the carb bodies for new shaft bushings.  I got some 5/16" ID and 3/8" OD bronze bushings from McMaster Carr.  I have a reamer that I purchased, but the particular reamer that I got was tough to use - the flutes were cut at the end so that pulling it back through the carb by hand was very difficult.  Frustrated,  I started thinking of how else to do this.  I thought of making a jig for my lathe - which is probably the best long-term solution - but came up with a way to do it on the drill press.

I took a piece of 1" thick maple and drilled a 5/16" hole through it.  I counterbored a hole for a bolt head on the back.  I then glued (using gorilla glue) a 5/16" bolt through the hole so that it when the board was sitting on the drill press table, the bolt shank was standing like a flagpole, over which you can slide the carb bodies through the thottle shaft holes.  Cut the bolt off so that it is just long enough to pick up the very bottom lip of the "upper" hole.  Be careful to square the drill table to the bit, then position the fixture so that the tip of the bit touches the middle of the new post you made.  Clamp the board to the table in this position.  Then, with the carb body in place, drill you centralized 3/8" hole - or actually use 23/64" first to make sure you get a tight fit.  Then, flip the carb body over and repeat.  The holes you drilled will have a shoulder where the drill did not go all the way through the aluminum, as the bit will stop when it hits the steel post. 

I'll post pics today.  I did a pair of carbs this way, and it worked very well.  Pics to come.

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